The present invention relates generally to ink coatings for use in the production of multiple copies from a single original or master. More particularly, the present invention concerns a low-cost transfer ink coating for use on transfer sheets used in the production of pressure transferable master sheets from which a multiplicity of high-quality copies may be printed.
Various techniques heretofore have been used in the production of multiple copies from a single original or master. Perhaps the best known example of such prior art techniques is the use of sheets of conventional carbon paper between the ribbon copy and one or more carbon copies in a typewriter. The fact that no master is used in the carbon paper technique limits the number of prints obtainable by such technique to the number of carbon paper-carbon copy layers which may be physically stacked together and accommodated in a typewriter carriage.
In addition, carbon paper is often messy to use and difficult to align for multiple carbon copies. The number of legible, clear copies resulting therefrom is further limited by the impact pressure of the tyewriter key striking the ribbon copy and the diminishing thereof by each subsequent layer of the carbon paper-carbon copy in a layered stack. The lower copies in a stack of multiple layers of carbon paper-carbon copy are poor in quality and relatively non-permanent. Accordingly, only a relatively few carbon copies of any legibility or usefulness may be produced by the carbon paper technique.
Furthermore, carbon paper techniques are less than satisfactory for non-typewriter applications, where large or oddly shaped print images are frequently required. Plainly, conventional carbon paper techniques would be quite unsatisfactory for use in areas such as the production of patterns for making dresses, suits, shirts and blouses or other clothing. In such areas the cost for labor, if carbon paper were to be used, would be uneconomically excessive, the legibility would be poor, and the low-quality copies produced therefrom undoubtedly could later smear on the fabric.
Other techniques of producing multiple copies have been devised for improving upon the carbon paper technique. The xerographic process is one such method. However, the initial capital outlay involved is quite large. Also, if the size of the copies sought to be obtained is larger than a given standard size for any particular machine, cutting and pasting techniques would be necessary, which is time consuming and produces messy, inaccurate copies at an excessively high cost.
Other techniques, such as offset printing, mimeographing diazo dye and spirit duplicating have also been utilized in an attempt to find an inexpensive alternative technique of producing multiple copies of any given size of shape, which copies would be sufficiently permanent and stable for use in the pattern making industry. Of these, offset printing would require sophisticated machinery and a high degree of labor skill, which would increase its expense to prohibitive levels in an industry which deals primarily with a low-cost, high-volume item.
Spirit duplicating techniques have heretofore generally been the most successful of prior art techniques for producing multiple copies of large or irregular sizes and shapes, such as would require in pattern making. In that technique, typically a stylus was used to trace a path on the back surface of a transfer sheet having the front surface coated with a transfer coating. Along such traced path, the pressure of the stylus transferred such coating to the surface of a spirit master sheet placed below and in contact with the transfer sheet. The spirit master sheet was then separated and several spirit-moistened copy sheets were serially pressed into contact with such spirit master. When separated, the spirit-moistened copies retained on their surface a portion of the ink design created by such traced path on the spirit master. The copies then had to be dried. However, in applications such as pattern making the copies sometimes were less clear than with direct printing techniques because of the tendency of the spirit to run during imprinting after separation and prior to drying on the large sheets used.
Also, the dyes used had to be soluble in the spirit. Additionally, some spirit soluble dyes proved to be of lower tinctorial strength than certain dyes otherwise available, but which could not be used because of their nonsolubility in the spirits required. Further, because of the spirit solubility requirements, the dye system utilized had to be applied to the spirit master in a dry or solid state. In order to accomplish this, resin binders were often necessary, which increased the cost of the transfer ink coating in such application areas as pattern making.